1. Field of the Invention
The invention relates to a lens, and more particularly to a zoom lens.
2. Description of the Related Art
In the well-known technology, for example, Japanese publication number JP 2005-345714, a zoom lens including six lens groups is disclosed, and the lens groups which are arranged in sequence from an object side to an image side are respectively with positive, negative, positive, positive, positive and positive refractive power. The effective focal length of the zoom lens is changeable when the second, the fourth and the fifth lens groups are moved. Japanese publication number JP 2008-304708 discloses a zoom lens including five lens groups and the lens groups which are arranged in sequence from an object side to an image side are respectively with positive, negative, positive, negatives and positive refractive power. Japanese publication number JP 2011-232543 discloses a zoom lens including five lens groups and the lens groups which are arranged in sequence from an object side to an image side are respectively with positive, negative, positive, negatives and positive refractive power. The effective focal length of the zoom lens is changeable when at least one of the first, the second, the third lens group is moved. The zoom ratios of the above zoom lens are all smaller than 16 times.
However, the requirement for zoom ratio of the zoom lens has been rising. A zoom lens with 16 times zoom ratio cannot meet the requirement of market. If the above three well-known technologies are used to design a zoom lens with about 24 times zoom ratio, miniaturization and good optical performance cannot be simultaneously achieved.